It is known from U.S. Pat. No. 3,755,419 to prepare 2-butenedioic acid or a derivative thereof by reacting acetylene with carbon monoxide and an alcohol in the presence of a palladium compound having a strong acid residual group, an amino acid and a heavy metal salt. The examples of this known process show that the 2-butenedioate esters were obtained in a low yield, calculated on starting acetylene. Moreover, an appreciable part of the esters formed consisted of the trans configuration, dimethyl fumarate.
It is an object of the present invention to prepare diesters of 2-butenedioic acids in a very high yield. Another object of the present invention is to obtain such diesters for a very large part in the cis-configuration.